GOPROXY is already used. It has nothing to do with gathering data, the proxy is a cache to store packages so you don’t need full git clones every time. By default, Go will use Google’s package cache, but with GOPROXY you can specify your own. If anything, GOPROXY is more privacy friendly, not less.
SSH traffic is practically impossible to cache, but GOPROXY allows for packages hosted on smaller services to be consumed by millions without taking the server down during compilation.
As for their telemetry, after the first uproar they seriously cut back on the amount of data they’re gathering. They have added telemetry… and made it opt-in, with some levels of indirection to make it more difficult to identity individuals.
There’s always some level of Googleness in this stuff, but I don’t think the ad people that push the Chrome and Android people into making worse products know that the Go people even exist.